This disclosure relates to methods of servicing a wellbore. More specifically, it relates to servicing a wellbore with a relative permeability modifier.
Natural resources (e.g., oil or gas) residing in the subterranean formation may be recovered by driving resources from the formation into a wellbore using, for example, a pressure gradient that exists between the formation and the wellbore, the force of gravity, displacement of the resources from the formation using a pump or the force of another fluid injected into the well or an adjacent well. The production of fluid in the formation may be increased by hydraulically fracturing the formation. That is, a treatment fluid (e.g., a fracturing fluid) may be pumped down the wellbore at a rate and a pressure sufficient to form fractures that extend into the formation, providing additional pathways through which the oil or gas can flow to the well.
Subsequently, oil or gas residing in the subterranean formation may be recovered by driving the fluid into the well using, for example, a pressure gradient that exists between the formation and the wellbore, the force of gravity, displacement of the fluid using a pump or the force of another fluid injected into the well or an adjacent well. The production of the fluid in the formation may be increased by hydraulically fracturing the formation. That is, a fracturing fluid may be pumped down the casing to the formation at a rate and a pressure sufficient to form fractures that extend into the formation, providing additional pathways through which the oil or gas can flow to the well. Unfortunately, water along with oil or gas may eventually be produced by the formation through the fractures therein. In such cases, the formation may be treated with a relative permeability modifier (RPM) that is meant to control water production, shut off water-producing intervals, and/or enhance hydrocarbon production. A particularly effective RPM material for such applications includes water-soluble polymers that are hydrophobically modified with suitable hydrocarbon groups.
A challenge to the use of hydrophobically modified RPMs (HMRPMs) is that some of HMRPMs lose their effectiveness to control or shutoff water production under certain conditions including, for example, the temperature at a downhole pH and salinity exceeding the lower critical solution temperature (LCST) of the polymer. For example, at temperatures greater than about 140° F. and at a pH of greater than about 7, some HMRPMs may precipitate out of solution limiting their effectiveness as relative permeability modifiers. Precipitation of the RPM not only substantially terminates its relative permeability-modifying properties, but also can damage a subterranean formation if the precipitation occurs downhole. Thus, an ongoing need exists for improved compositions and methods for utilizing RPMs in subterranean formations.